Method of conditioning a rotatable lap



gli-iq. E.

Dec. 22, 1964 R. G. RosHoNG 3,131,996

METHOD OF CONDITIONING A ROTATABLE LAP Filed March 25, 1954 2 Sheets-Sheet 2 O IQ chum Rfim) United States Patent O 3,161,996 METHOD F CNDITlONNG A RGTATABLE LAP Raymond G. Roshong, North Hollywood, Calif., assignor to Crane Packing Company, Chicago, lll., a corporation of illinois Filed Mar. 2S, 1954, Ser. No. 418,647 Claims. (Cl. 51--281) The present invention relates to lapping machines for i lapping and surfacing various products of manufacture as for example the annular surfaces of rotary mechanical seals, thrust washers, piston rings, flat valve faces, gage blocks, piezoelectric crystals and a large variety of other :dat work too numerous to mention, and particularly to a method of conditioning the lap of such machine as to contour.

More particularly, the invention relates to lapping machines of the general type wherein there is provided a rotatable lap having a substantially fiat lap surface on which there is positioned one or more wear rings each of which is adapted to overlie the lap annulus and overhang both the inside and outside peripheral edges of the annulus, together with means for preventing revolution of the wear ring or rings about the axis of the lap. Such a machine has been shown and described in my prior Patent 2,627,144, dated February 3, 1953, for Lapping Machine.

In the machine illustrated in my above mentioned patent the means for preventing revolution of the wear rings about the axis of the lap annulus is also employed for the purpose 'of adjusting the position of the wear rings radially toward and away from the axis of the lap so that the lap surface will be automatically dressed during lapping operations under controlled conditions whereby the lap annulus may volitionally be caused to assume a required convex, concave or plane surface. In the machine Villustrated in this patent the extent of overhang of the wear rings on either the outside or inside edge of the lap annulus is the controlling factor for effecting lap dressing operations. If the overhang is greater at the outside than at the inside, the unbalanced force will tend to wear the lap convex. Conversely, if the amount of overhang at the inside is the greater, the lap will tend to become concave. Where the overhang is equal a fiat lap annulus will be maintained.

The present invention contemplates a different principle of lap dressing operations based upon the expedient of positively rotating or driving the wear rings at varying rates of speed about their own vertical axes, either in the normal direction of induced rotation or in the opposite direction, while at the same time maintaining a constant amount of overhang both at the inside and at the outside circular edges of the lap annulus. This method of controlling the contour of the lap annulus is predicated upon tile principle that by varying the differential between the velocity of the wear ring and the lap annulus at different radial distances from the center of the lap, different frictional characteristics will be attained at radially spaced regions of the lap annulus thus creating a wear diiferential at these regions.

It is therefore among the principal objects of the present 3,161,996 Patented Dec..v 22, 1964 lCe between the Wear ring and the lap surface at radially spaced points with reference to the lap annulus.

Other objects and advantages of the invention not at this time enumerated will become more readily apparent as the nature of the invention is better understood.

In the drawings,

FIG. 1 is a perspective view of a lapping machine constructed in accordance with the principles of the present invention,

FIG. 2 is an enlarged fragmentary perspective View of the top or table portion of the machine in the vicinity of the lap annulus,

FIG. 3 is a sectional view taken substantially along the vertical plane indicated by the line 3 3 of FIG. 2, and

FIG. 4 is a circuit diagram for the machine.

Referring now to the drawings in detail, the invention is shown as being applied to a lapping machine of the type intended for lapping fiat work such as the running faces of rotary mechanical seal elements. The machine involves in its general organization a stationary framework 1t) of table-like design and including a table top 12 having apron-like sides 14 and depending supporting legs 16. Projecting upwardly through a circular opening 18 in the table portion l2 is a rotatable lap plate 20 preferably formed of cast iron or other suitable material and having an annular abrading surface 22 provided with a series of radially disposed slots 24 which serve to carry away excess abradant as Well asfthe cuttings resulting from the abrading operation. A motor Ml (FIG. 4) is provided for rotating the lap plate 20.

The upper surface or annulus 22 of the lap plate 26 is adapted to receive thereon a plurality of wearrings 26, three such ringsbeing shown for illustrative purposes. These wear rings 26 are preferably formed of the same material as the material of the lap plate, i.e. cast iron, and the rings are of such diameter that they may be positioned on the lap annulus so as to overlap slightly both the inner and outer peripheries 28 and 30 respectively as clearly shown in FIG. 3. These wear rings 26, which sometimes are referred to as conditioning rings, are adapted to rest frictionally on the surface of the lap annulus and means are provided for preventing them from riding with the lap, so to speak, or in other words, for holding them against revolution about the axis of the lap plate so that each ring is held permanently within its own quadrant of the lap annulus. In order to thus support the rings against revolution about the lap axis each ring has secured thereto an inverted U-shaped yoke 32 which may be secured to the upper rim of the wear ring by means of anchoring screws 34 and which assumes a diametric position with respect to the wear ring. Each yoke 32 is formed with a squared opening 35 centrally therein into which there projects the squared portion 36 of a vertical drive shaft 38. The various drive shafts 38 are adapted to be driven in unison at varying rates of speed in order to impart their rotary motion to their respective wear rings to thus control the contour of the lap annulus as between convex, flat and concave all in a manner that will be made clear presently.

A small or limited amount of universal oating movement is permitted between each Wear ring 26 and the vertical axis of its respective drive shaft or spindle 35 so that the wear ring will at all times rest squarely upon the opening in the yolre member 32 constitutes but one ofV numerous ways in which the wear ring may be driven while allowing for slight limited universal movement of the ring. Among the other driving means which are contemplated is the use of splines on the drive shaft or other suitable keyed arrangements.

Thev

ably supported on a platform 11e mounted on the tank 1w. The liquid contained within the tank lltl and in which the particles of grit are held in suspension is adapted to flow outwardly through a discharge orifice 117 (FlG. 4), the opening and closing movements of which are conducted by means of a solenoid actuated valve 118.

From theoritce this-grit laden fluid may iiow along a Spaced above the general plane of the lap annulus and overlying the latter is a horizontally disposed spider all including a shank portion 42 and three spiderrarms d4, 45 and 48. The spider 41D is supported above the lap plate in spaced relation with respect thereto by means of a vertical post Su which extends upwardly from the table portion 12 of the framework 16 and which receives thereover a sleeve 52. The'upper end of the sleeve 52 is provided with a recess 54 therein in which recess there is seated the free end of the shank 42 of the spider 40. The upper end of the post S is threaded as at56 and is adapted to receive thereon a clamping nut and washer assembly S by means of which the shank 42Vmay be anchored to the y post 50 in a horizontal position. The free end of each spider arm 44, 46 and 48 is formed with auenlarged -boss 60 in which one of the vertical drive shafts 3S is rotatably journaled. The upper end of eachdrive shaft 3S has .mounted thereon a drive pulley 62 and the various drive pulleys are operatively connected together in driving relationship by means of a drive belt 64 which passes around these pulleys.

One of the drive shafts 38 has mounted thereon a relatively large pulley 66, this latter pulley being operatively connected by means of a driving belt 6h to the split sheave 70 of a conventional Reeves drive mechanism designated in its entirety at 72,. The mechanism 72 includes the usual spring housing mand torque-receiving ,pulleyl 76. The split sheave 70 and pulley 76 are mounted on a shaft 7S which is rotatably journaled in a casing Sil supported at the upper end of a bracket 82. .The bracketSZ is secured by means of screws 33 to a vertical post Sd which in turn extends upwardly fromv the table top 12;

A horizontally extending guide bar @il projects laterally from the supporting past 84 and has a sliding dove-tail connection as at 92 with a horizontally movable supporting vblock 94', the block being movable in opposite directionstoward and away from the supporting post S4. The block 94 has mounted thereon an electric driving motor M2 which is preferably of the reversible type. The motor -M2 is provided with a drive shaft 96 which projects vertically upwardly from the motor casing and which carries thereon a driving pulley 9S which is operatively connected by means of a drive belt 160 to the driving pulley 76 of the Reeves variable speed drive mechanism 72.

lIn order to move the block 94 and consequently the motor M2 horizontally along the guide bar 90, a strut 102 extends across the guide block 94 and is provided with'a threaded opening 1M therethrough which threadedly receives a worm shaft 106, one end of which is formed with an enlarged head 19S rotatably journaled in the bracket 82. The worm shaft 105 extends completely through the strut 162 and carries at its free end ahand Wheel 109-by means of which rotational movements may be imparted to the worm shaft 166.

It is essential to the operation of a machine of this charactor that the surface of the lap plate 2l) be supplied with a lap compound consisting of a gritty duid including a suitable vehicle in which particles of grit or abrasive are maintained in suspension. Accordingly, means are provided for supplying and distributing such a lapping comy pound over the rotating lap annulus 22 and, toward this llexible wire 12@ leading to a point adjacent one of the Wear rings 26. The free end of the wire 12"?? may bear livhtly against the side of the wear ring so that the iluid will be conducted to the ring and then distributed over the surface of the rotating lap plate as the latter passes beneath the wear ring. A housing 122 mounted on the table portion 12 serves to support the agitator tank 110 as well as to contain certain electrical control instrumentalities associated with the machine and the nature of which forms no part of the present invention and which will be discussed only briefly herein.

The electrical components of the :present machine consist of the motor M1 for driving the lap plate 2u, the motor M2 for driving the wear rings 25, the motor M3 which operates the agitator mechanism and the solenoid valve 11S which controls the llow of lapping compound along the feed wire 12u. These major components are shown diagrammatically in FIG. 4 but are not specifically described since they have no special significance insofar as the present invention is concerned. As shown, the

' motors M1, M2 and M3 are larranged in a parallel circuit lto drive the various wear rings 26 in a selected direction,

for example in a counter clockwise `direction which is the same as the direction of rotation of the lap plate 26). The switches S1, S3 and S4 are closed to cause rotation of the lap plate, operation of the agitator mechanism, and opening of the orifice 117 whereupon the machine will be set into operation. As the lap plate 2li rotates at a uniform rate of speed in a counter clockwise direction as seen -in both FIGS. l and 2, such rotation thereof will tendy to induce rotation in the various wear rings 26 due to the fact that the outer peripheral speed of the lap plate is greater than the inner peripheral speed thereof so that consequently greater frictional forces are developed between the lap plate and the wear rings in the outer regions of the plate than are developed in the inner regions thereof. This tendency for induced rotation is such that each of the wear rings will be constrained to rotate in a counter clockwise direction about its own vertical axis. For theoretical considerations, let it be assumed that the various wear rings are free rotating members. In such an instance a predetermined rate of induced rotation would ordinarily be set up in each of the wear rings and the abrading effect upon the lap would then be dependent to a large extent upon the respective amounts of overhang existing between each wear ring and the lap at the inner and outer edges 23 and 30 respectively of the lap annulus. Obviously, if a greater overhang exists at the outer periphery than at the inner periphery, the tendency for the lap surface will be to gradually assume a convex contour. Conversely, if the overhang at the inner edge of the lap is greater than at the outer edge thereof, the tendency for the lap will be to gradually become concave. It follows therefore that there must be a medial radial position for each wear ring wherein the surface of the lap plate will remain substantially frat over a prolonged period of time. It is believed that this medial position is such that the amounts of overhang at the inner and outer edges 2d and 3u of the lap are substantially equal. Under such conditions, and with no work being operated upon within the contime. The localized abrasion caused by such work may tend to Wear the lap out-of-at and, in such an instance, corrective measures must be taken to bring the lap annulus back to its condition of atness. As stated above, in connection with my prior Patent 2,627,144, this correction ordinarily is performed by shifting the position of the wear rings inwardly or outwardly as the case may be. However, according to the present invention, such corrective measures are obtained by either positively accelerating or positively decelerating the rate of rotation of the wear rings or, in certain instances, by effecting rotation thereof in the opposite direction, i.e. in a clockwise direction. If there is a tendency for the lap plate to become convex for example, an increase in the speed of rotation of the wear rings from their normal rate of induced rotation will tend to bring the surface of the lap plate back to its condition of flatness. This is true because, as seen in FIG. 3, the portions of a wear ring which slide over the surface of the rotating lap plate near the outer periphery thereof will have linear components of motion which are in the same general direction as the linear components of motion of portions of `the lap plate with which they are in contact, whereas the contacting portions near the inner periphery of the lap will have linear components of motion which generally are in the opposite direction. An increase in rotational speed of the wear ring will therefore present a greater speed differential between the two running surfaces near the inside of the lap annulus and greater abrasive factors will come into existence at this inner region. Conversely, a decrease in the rotational speed of the wear ring will have an opposite effect and the rate of change from a normal abrasive action near the outside of the lap annulus will be greater than the rate of change from the normal abrasive action near the inside of the lap annulus.

From the above description it will be obvious that if, after the machine has been in actual operation for a given length of time, it is found that the lap plate tends to become convex, corrective measures may be taken by adjusting the hand wheel 109 in an appropriate direction so as to cause the block 94 to move outwardly on the guide bar 90 to thus actuate the Reeves variable speed drive mechanism 72 so as to increase the rate of rotation of the pulley 66 and consequently of the drive pulleys 62 for the three conditioning rings 26. The net result of this will be to increase the rate of rotation of the conditioning rings so that they will continue to rotate at a speed somewhat in excess of their normal induced rate of speed. If the conditions which in the iirst place caused the lap plate to become convex remain in effect, the corrective measures which were put into effect by adjustment of the hand wheel 109 may be allowed to operate until such time as the lap plate is again restored to its normal flat condition. When this has been accomplished, a new setting for the hand wheel calculated to maintain the lap annulus ilat for the given set of conditions may be made. Obviously, the appropriate setting of the hand wheel 109 at any given instant, or during any given interval lof time, will be made according to the judgment, skill and experience of the operator who will take into consideration the character of the work undergoing lapping. A

It is obvious that if the lap plate is found after a period of operation to have become concave, actuation of the hand wheel 109 in the opposite direction so as to cause the block 94 to move inwardly on the guide bar 90 will decrease the rate of rotation of the various wear rings 26 and this decrease in the speed of rotation may be continued until the wear rings rotate at the rate of speed which is something less than the normal speed of induced rotation thereof. As explained above, the frictional forces acting between the wear rings and the lap annulus will in such an instance tend to restore the lap annulus to its condition of atness.

In certain instances, as for example where an abnormal condition of concavity obtains, the reversing switch S2 may be operated so that the motor M2 will drive the various wear rings 26 in a clockwise direction .at a predetermined rate of speed operable under the control of the hand wheel 109. In such an instance high frictional forces lwill be developed in the outer regions of the lap and comparatively lower frictional forces will be developed in the inner or central regions of the lap producing an abrasive differential at these inner and outer regions which is comparatively great and which will tend to rapidly restore the lap annulus to its condition of atness.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes inL the form and details of the lapping machine illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What I claim and desire to secure by Letters Patent is:

1. The method of controlling the contour as to atness, convexity, or concavity of the operating surface of a lap plate rotating about a fixed axis, by means of a rigid dressing tool which comprises positioning the tool to rest upon the lap surface, constraining the tool to rotate about an .axis eccentric to the axis of rotation of the lap while allowing the tool to move through an angle with respect y to the axis of the lap so that the dressing face of the tool may follow the contour of the lap, positively rotating the tool about its axis, and regulating the linear velocity between the contacting lap and tool surfaces to produce different degrees of wear of the lap surface by the tool along a radius of the lap surface.

2. The method of changing the contour of an annular lap rotatable about an axis passing through the center of the lap, comprising abrading the lap by a tool which rests upon the lap and extends across only the radial dimension thereof, said tool taking its position from the lap surface contacted thereby, rotating the lap at a predetermined speed about its axis, said rotation of the lap at said predetermined speed inducing a rotation in the tool about the tool axis at a slightly different speed and thereby producing both a dressing and a contour shaping effect upon the lap surface, and superimposing upon said induced rotation a positive drive at a speed other than the said slightly `different speed whereby to change the contour shaping eifect produced by the induced tool rotation.

3. The method of changing the contour of an annular lap as described in claim 2 wherein the speed of the positive drive is greater than the induced speed whereby to increase the dressing action of the tool at radially inner regions of the lap surface and decrease the said dressing action at the radially outer regions of said surface.

4. The method of changing the contour of an annular lap as described in claim v2 wherein the speed of the positive drive is less than the induced speed whereby to decrease the dressing action of the tool at radially inner regions of the lap surface and increase the said dressing action at the radially outer regions of said surface.

5. The method of correcting the dressing action of an annular tool operating upon a radial region only of rotating annular lap, wherein the tool rests upon the lap surface so as to be positioned thereby and has a rotation about its axis induced therein by its contact with the lap,

the axis of rotation of the tool being radially offset from the location thereof at which uniform Wear is produced by the tool over the entire surface of the lap such that the initiall contour of the lap surface is progressively changed, which method comprises driving the tool at a higher speed than the speed of the induced rotation when the induced rotation tends to cause Wear of the radially inner regions of lthe lap surface faster thanhe radially outer regions, and at a lower speed than the speed of the kinducedrotation when the induced rotation tends to cause Wear ofthe radially inner regions of the lap surface slower than Lthe radially outer regions.

References (ed in the le of this patent Re. 23,937 765,105 2,136,036 2,269,071 2,391,388 2,565,590 2,627,144y

UNITED STATES PATENTS Bullard Feb. 8, 1955-' Setter July 12, 1904 Avery Nov* 8, 1938 Bullard July 23, 1940 Bullard Dec. 25, 1945 Bullard Aug. 28, 1951 Roshong Feb, 3, 1953 Wolfskill Apr. 14, 1953 

1. THE METHOD OF CONTROLLING THE CONTOUR AS TO FLATNESS, CONVEXITY, OR CONCAVITY OF THE OPERATING SURFACE OF A LAP PLATE ROTATING ABOUT A FIXED AXIS, BY MEANS OF A RIGID DRESSING TOOL WHICH COMPRISES POSITIONING THE TOOL TO REST UPON THE LAP SURFACE, CONSTRAINING THE TOOL TO ROTATE ABOUT AN AXIS ECCENTRIC TO THE AXIS OF ROTATION OF THE LAP WHILE ALLOWING THE TOOL TO MOVE THROUGH AN ANGLE WITH RESPECT TO THE AXIS OF THE LAP SO THAT THE DRESSING FACE OF THE TOOL MAY FOLLOW THE CONTOUR OF THE LAP, POSITIVELY ROTATING THE TOOL ABOUT ITS AXIS, AND REGULATING THE LINEAR VELOCITY BETWEEN THE CONTACTING LAP AND TOOL SURFACES TO PRODUCE DIFFERENT DEGREES OF WEAR OF THE LAP SURFACE BY THE TOOL ALONG A RADIUS OF THE LAP SURFACE. 